The present technology relates to an optical system that is capable of performing close-distance shooting that is a so-called macro lens that may be desirably capable of shooting an object at infinite to an object at a close distance with equal shooting magnification and that has high imaging performance. In particular, the present technology relates to a macro lens that is used in an apparatus such as a still camera, a video camcorder, and a digital camera, and also relates to an imaging unit that uses such a macro lens.
In recent years, an imaging unit that is capable of shooting both a still image and a moving image by one imaging unit has been widely spread particularly in shooting with the use of a digital camera. For a lens for shooting used in such an imaging unit, not only higher speed of a focusing operation at the time of shooting a still image but higher speed of a focusing operation at the time of shooting a moving image has been desired since images are recorded almost all the time even during the focusing operation in shooting a moving image. In particular, an imaging unit has been widely used that has an automatic focusing mechanism of a contrast detection type. Therefore, in a lens for shooting that is used in such an imaging unit, there is provided a lens group, a so-called wobbling lens group, that slightly travels along an optical axis in order to detect a focusing position by contrast. It is to be noted that, since the focus lens group and the wobbling lens group both operate to allow the focal position to vary along the optical axis, one lens group has both functions and the focus lens group is not distinguished from the wobbling lens group in many cases.
In a so-called macro lens that is capable of performing a focusing operation from an object at the infinite to an object at a close distance with equal shooting magnification, a traveling amount of the focus lens group that travels at the time of performing the focusing operation is likely to be large. Therefore, in order to achieve a high-speed focusing operation by a focus motor, it is desirable to reduce the weight of the focus lens group. Further, when the focus lens group also serves as the wobbling lens group, higher speed is desired in operation. Therefore, it is further desirable to reduce the weight of the focus lens group. As such a macro lens, a macro lens is proposed that has five lens groups and three lens groups out of those five lens groups are used to perform the focusing operation (for example, see Japanese Unexamined Patent Application Publication No. 2011-048232).